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| [GMCnet] What a Day! [message #77400] |
Sat, 20 March 2010 21:38  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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What a day this has been. After a couple of days of staying away from the
GMC, I decided it was time to try to get it going. So I went through all of
the VSS & CCD wiring I added to the 455 before moving the Howell EFI to the
Cad 500. Everything checked out, by continuity, except that I'd swapped the
labels on two of the CCD leads -- ONLY the labels; the leads were correctly
wired.
So I cleared error codes started it up. It seemed to run fine, despite the
EC 43 (ESC) error which immediately reappeared. So I began my 25 mile test
loop. About 11 miles into it, the engine suddenly died; I coasted to the
shoulder of the two lane road about 1/4 mile beyond an active repaving crew,
on the steepest up grade in this area (maybe 3%). After checking everything
I could think of, I attempted to restart the engine and got only a thunk.
With the boost switch ON, I still got only a thunk and the voltmeter
dropped to 6-8 volts. While I'd been watching the new CS130D alternator
charge at 14 VDC, I know all my batteries are near the end of their useful
lives.
With no luck cranking, I called HER to bing the S-10 with the jumper cables.
She arrived in 1/2 hour or so, bringing my slightly overdue lunch of bbq
chicken. Before eating, I had HER hit the starter while I held the
voltmeter leads directly on the battery terminals. The voltage there
dropped very low, unboosted and boosted, just like on the dash meter, so I
knew the problem was not due to a bad connection. With the jumpers to the
S-10 and its engine revved up, the Cad fired right off -- but ran terrible.
Since it was only 1/2 mile or so to my aunt's farm, I nursed the GMC there,
very slowly -- couldn't do otherwise. While eating my lunch, the hospital
called to say that they were ready to release my mother. So, we packed up
and took the S-10 home, where I changed to a clean shirt. Taking the sedan,
we went and picked Mother up at the hospital and got her settled back into
her Assisted Living room at the retirement community.
Back at the farm with the S-10, I tried the GMC again -- it fired right up
and ran somewhat better than it had when we arrived. Even though the farm
is completely secure, and has a barn full of tools, plus 'most anything else
I might need, I decided to try to make it the 12 miles home with the GMC.
Big Mistake!
About 2 miles from the farm, the engine began to run badly again. By 4
miles, it was running terrible. At 5 it quit completely -- on the worst
curve in the county, where there is no significant shoulder. With half of
the coach in the road, I scrambled to get it running -- to no avail. Even
with S-10 help to start it, the engine had no power when running. With the
farmer from across the road entertaining HER with horror tales about
accidents on that curve, the pressure was really on (despite the fact that
heavy traffic there is a truck every 5 minutes or so). As much as SHE HATES
it, SHE didn't hesitate when I hooked the 10,000# test nylon rope between
the S-10 and the GMC and told HER to tow me off of the curve and to stop
when I blew the horn. With the little help the GMC could provide, the S-10
was able to get us moving and proceed at 15-20 mph for about 2 miles to a
wide shoulder on a straight stretch of road. SHE didn't hear the horn, but
I stopped anyway (the terrible-running engine, helped by the boost pump and
the reservoir did provide brake vacuum). Only a little section of the rope
was sacrificed.
After 1/2 hour or so of trying, it became obvious that I wasn't making any
progress. By tinkering with the ignition timing, I was able to get enough
power out of the engine to maneuver the coach across the road into a
farmer's wide driveway, where we left it for the night (with permission).
Some may recall that during the initial engine run-in I had to replace the
iginition module. Now I suspect that the coil may also be defective --
perhaps having caused the module failure? I'm also suspecting the
replacement module. And I'm thinking that something is advancing the timing
during starting, causing an excessive load.
At any rate, my plan for tomorrow, unless someone proposes a more attractive
one, is to replace the CCD with the original mechanical/vacuum distributor
which I got with the engine. I just checked the weights for freedom of
movement and the vacuum with a Mity-Vac; everything seems OK. Merely
replacing the distributor, removing the ESC module, and reconnecting the
Howell Tach Buffer should put me back in commission, IIRC.
Ideas gladly considered.
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] What a Day! [message #77407 is a reply to message #77400] |
Sat, 20 March 2010 22:31  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Idea----Rochester Quadrajet.
No really, put some decent batteries in there at least the engine one. How can you expect a computer vehicle to run right without stable full voltage. If the engine batt is that bad not to crank it, how can it act to smooth out the rough choppy DC from the alternator so the computer has constant voltage. Hey you have to replace the group 78 batt anyway so why not start there.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] What a Day! [message #77411 is a reply to message #77407] |
Sat, 20 March 2010 22:53 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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John,
I really don't expect any improvement in running with a different battery.
The CS130D alternator ('99 technology, MUCH cleaner output than '76
technology) I'm using was, from all appearances, producing full 13.8-14.0
VDC whenever the engine was running, regardless of the condition of the
batteries. I did, in fact, run some of the time with the engine battery
disconnected, with Boost ON, to be sure it was not loading the system. With
all batteries connected, selecting or deselecting Boost had no visible
effect on the dash voltmeter -- regardless of which battery it was
monitoring.
It appears to me that the distributor or ECU was causing the timing to be so
advanced that the starter could not overcome early ignition of the mixture
-- that's the only thing that makes sense to me right now.
Ken H.
On Sat, Mar 20, 2010 at 11:31 PM, John R. Lebetski <gransport@aol.com>wrote:
>
>
> Idea----Rochester Quadrajet.
> No really, put some decent batteries in there at least the engine one. How
> can you expect a computer vehicle to run right without stable full voltage.
> If the engine batt is that bad not to crank it, how can it act to smooth out
> the rough choppy DC from the alternator so the computer has constant
> voltage. Hey you have to replace the group 78 batt anyway so why not start
> there.
> --
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| Re: [GMCnet] What a Day! [message #77412 is a reply to message #77407] |
Sat, 20 March 2010 23:01 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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| JohnL455 wrote on Sat, 20 March 2010 20:31 |
Idea----Rochester Quadrajet.
No really, put some decent batteries in there at least the engine one. How can you expect a computer vehicle to run right without stable full voltage. If the engine batt is that bad not to crank it, how can it act to smooth out the rough choppy DC from the alternator so the computer has constant voltage. Hey you have to replace the group 78 batt anyway so why not start there.
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I am with John. I keep thinking voltage. It ran really crummy after you jumped it. My theory is the computer voltage went so low it lost its memory and the BLM tables had to be re-created. You say you had 14 volts, but it sure sounds like it was running out of juice again as you started back.
Here is another thought. I don't remember what year HEI started, but the early points distributor had a resistor that reduced the voltage to the coil and in HEI the module. I was told I had to run a fresh switched 12 volts to the batt terminal on the distributor on my 74. Could it be that the PO didn't do this when it was switched to HEI? (Do we have 12 volts nominal at the batt connection?)
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: [GMCnet] What a Day! [message #77414 is a reply to message #77412] |
Sat, 20 March 2010 23:22 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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George,
I'll replace the chassis battery, just in case. But the initial failure,
and subsequent bad running, occurred when the voltage was being maintained
by the alternator. Remember that the CS130D is capable of producing 80A at
a rotor speed of 3000 rpm -- about 1100 engine rpm!
My '76 was delivered with HEI so never had a ballast or resistance wire --
besides the fact that I've replaced all that wiring.
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
On Sun, Mar 21, 2010 at 12:01 AM, George Beckman <gbeckman@pggp.com> wrote:
>
>
> JohnL455 wrote on Sat, 20 March 2010 20:31
> > Idea----Rochester Quadrajet.
> > No really, put some decent batteries in there at least the engine one.
> How can you expect a computer vehicle to run right without stable full
> voltage. If the engine batt is that bad not to crank it, how can it act to
> smooth out the rough choppy DC from the alternator so the computer has
> constant voltage. Hey you have to replace the group 78 batt anyway so why
> not start there.
>
>
> I am with John. I keep thinking voltage. It ran really crummy after you
> jumped it. My theory is the computer voltage went so low it lost its memory
> and the BLM tables had to be re-created. You say you had 14 volts, but it
> sure sounds like it was running out of juice again as you started back.
>
> Here is another thought. I don't remember what year HEI started, but the
> early points distributor had a resistor that reduced the voltage to the coil
> and in HEI the module. I was told I had to run a fresh switched 12 volts to
> the batt terminal on the distributor on my 74. Could it be that the PO
> didn't do this when it was switched to HEI? (Do we have 12 volts nominal at
> the batt connection?)
>
>
> --
> '74 Eleganza SE
>
>
> Best Wishes,
>
> George
> _______________________________________________
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>
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| Re: [GMCnet] What a Day! [message #77416 is a reply to message #77411] |
Sun, 21 March 2010 00:10 |
rvanwin
Messages: 325
Registered: April 2007
Location: Battlefield, MO
Karma: 6
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Senior Member |
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| GMCWiperMan wrote on Sat, 20 March 2010 22:53 |
It appears to me that the distributor or ECU was causing the timing to be so
advanced that the starter could not overcome early ignition of the mixture
-- that's the only thing that makes sense to me right now.
Ken H.
|
I didn't think it would be the battery because you said you had 14 volts when running, although I guess you must have a weak battery if you were able to jump it and get it to turn over. Once running, the ECU should work OK. Makes me wonder why the chassis battery didn't at least turn it over some. My boost doesn't seem to always work (need to track that down) so maybe yours didn't either. Usually too advanced while starting will get you a little turn of the engine before stopping - is this the case? Hate to bring this up, but I once had a Buick that wouldn't turn over -- it had antifreeze in one cylinder - blown head gasket.
I vote for the module and/or coil. Still thinking about the ESC problem....
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO
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| Re: [GMCnet] What a Day! [message #77425 is a reply to message #77414] |
Sun, 21 March 2010 06:03 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| GMCWiperMan wrote on Sat, 20 March 2010 23:22 |
George,
I'll replace the chassis battery, just in case. But the initial failure,
and subsequent bad running, occurred when the voltage was being maintained
by the alternator. Remember that the CS130D is capable of producing 80A at
a rotor speed of 3000 rpm -- about 1100 engine rpm!
My '76 was delivered with HEI so never had a ballast or resistance wire --
besides the fact that I've replaced all that wiring.
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
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I blew 2 HEI ignition modules on my coach withing a short period of time. On replacing the second module I also replaced the coil. I believe the coil was taking out the modules. That was many thousands of miles ago and I have had no problem since. If that distributor is HEI and has a bad module I would replace both the module and the coil.
On the battery, If it is bad it will not filter out the AC ripple from the alternator. A shorted diode or open in the alternator will also cause a problem with electronic devices. I have seen a weak battery cause alternator whine in installed ham radios. Replacing the battery gets rid of the alternator whine in the radio. I would replace the battery with a known good one. Also is the ground lead from the engine battery hooked direct to the engine block? If this continues to be a problem hook a scope on the battery and see if you have a lot of ripple. I once had an open winding on 3 phase transformer inside an IBM computer. I eventually found the problem with a scope. Replacing 40 to 50 pound transformer fixed that problem. When I ordered the transformer the IBM plant initially refused to ship it saying it could not be the problem. After arguing with me they did ship it overnight and it fixed the problem.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] What a Day! [message #77455 is a reply to message #77400] |
Sun, 21 March 2010 10:45 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I feel like I was bit of a wize guy with the Qjet remark so I hope no offense taken. I was just trying to weigh out the aggravation factor of an EFI system VS the 'go out and use and enjoy the motorhome factor' of a simple Qjet system. If it all works properly the EFI will run better/ more efficiently but will you ever recoop the effort. The flip side is if you are like me there is a lot of satisfaction in the end if you solve the problem.
On the Battery issue, even if your VOM whether A or D shows 14-14.2 or so (average) if you look at the waveform on a scope it should be 3 humps per rotation as the 3 PH AC is converted to DC internally by the diodes. If the batt impedance has gone high on a failed cell let's say, the computer may be seeing this as a constantly changing voltage which it is. The jumper cables/ house batt may be too 'far away' to give the desired smoothing effect. Could this put it in stupid mode? I know that one of the parameters on GMs was to raise the idle speed if voltage is perceived as low. It's probably not getting a good read if nothing else. Also, since most of the sensors take a constant voltage (known) from the computer and then use the difference to give the data back, this too could be a problem throwing it for a loop. I have no experience with aftermarket EFI so just applying the little I do know about OEM and theorizing. Hope you solve it and let us know.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] What a Day! [message #77507 is a reply to message #77400] |
Sun, 21 March 2010 17:14 |
WayneB
Messages: 233
Registered: July 2008
Location: Ontario, Canada
Karma: 0
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Senior Member |
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Load test the batterys, I am betting you will find they have a bad cell or cells.
They will show reasonable voltage but when you place a demand on them (amperage) they are breaking down internally.
This happens up here all the time in winter conditions, the electrolite in the battery will freeze and expand when its really cold, causing the internal plates to buckle and touch each other causing internal shorts.
Battery casings that are bulged out at the sides are normally a good indication this has occured.
1976 23' GMCII By Explorer
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| Re: [GMCnet] What a Day! [message #77543 is a reply to message #77507] |
Sun, 21 March 2010 19:20 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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Thanks, All, for all the good suggestions. I suspect those with battery
qualms are correct. But, before actually swapping out batteries, today I
just used the S-10's battery and alternator, through big jumper cables, to
continue searching for other problems. I also paralleled the S-10 battery
with a portable jump-start battery, to provide a little more capacity.
As planned last night, I re-installed the non-computer-controlled HEI that
came on the engine. That was another exercise in frustration: It wouldn't
even flash the timing light! After checking and rechecking my installation,
I gave up and drove the 8.7 miles back home with the distributor. There, I
gutted the Dick Paterson distributor from the 455 and used those known good
parts to rebuild the 500's HEI. Learned a couple more lessons -- such as
don't expect a 34 year old shaft to come out easily. When that one did, it
brought with it the upper bushing and the pickup coil, the retaining circlip
for which I had not removed (nor ever seen).
During that exercise I got a call from HER, informing me that Mother didn't
want to even get out of bed -- an untenable situation for her if she's to
stay in Assisted Living instead of being moved to the Nursing Home. But SHE
said for me to continue the GMC recovery and SHE'd handle the situation.
Which she did, as well as possible, considering...
After an hour or so, I had the 500's HEI reassembled with the Paterson
parts, and returned to the coach to install it. The location of the 500's
distributor is not as convenient as that on the Olds -- it's at the left
front, canted 45* toward the driver's side. There is no real good way to
orient it, especially with a vacuum advance can attached, and, worse yet,
with a top mounted A/C compressor. With the can oriented to the rear, which
is the only location that keeps the wires and hose safely away from the fan
belts, there's <45* of rotation room available for setting timing.
Before I rebuilt the HEI, I really could not set the initial timing to
exactly to the 10* BTDC that I wanted -- the vac. can hit the left forward
intake manifold bolt at about 9*. Shifting all the plug wires one position
created the opposite condition, so I left it that way -- until I found that
it wasn't working anyway. Then, with the HEI rebuilt, the 10* BTDC position
was at the middle of the available travel! I haven't yet figured out why --
maybe the mechanical advance was stuck and I didn't realize it.
When I hit the starter with the rebuilt HEI, the timing light loved it, and
the engine started right up -- and immediately died.
After a lot of start 'n' die episodes, I finally nursed the RPMs up to
1500+, where things smoothed out and I was able to do some more
troubleshooting. Including aiming the timing light at the throttle body
throats. Hmmmm...sure don't see as much gas from that right injector as
from the left... When my finger came back from the right throat with NO
gas on it, I began to get suspicious. Swapping the leads to the two
injectors proved that both injectors work fine. But the right one is not
being fired by the ECU. A quick continuity check to the connector showed
the wiring is OK. So I pulled the ECU cover and checked continuity all the
way from the injector to the PC board pin -- all good. :-( That means the
ECU's driver for the right injector has failed.
Take it from me: The Cad 500 does NOT make a good 4-cylinder engine! No
wonder that 4-6-8 thing didn't catch on. :-)
Tonight I'll check the schematic for the ECU; it may be possible to relocate
the connector pin for that injector to the location served by the other
driver (there are two for each injector, only one of which is used in our
application). I THINK both drivers in each pair are hard-wired together so
that they're both available for use with no software changes required. Sure
hope so, else I'll have to wait for my loaned-out spare to be returned
before I can recover the GMC.
The farmer in whose drive the coach is parked has not been home all day, so
I left him a note to call me. I hope he'll let me leave it there until I
can drive it the 8.7 miles to our place. I could use RV Roadhelp, but I
hate to do so in this situation.
Wonder why I'm so snake-bit on this project???
Oh yeah, with the thing running on 4 cylinders at 1500 rpm, I had a good
solid 14 VDC showing on the voltmeter -- but I did NOT have a 'scope on it
to check the waveform.
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
On Sun, Mar 21, 2010 at 6:14 PM, Wayne Barratt <waynebarratt@msn.com> wrote:
>
>
> Load test the batterys, I am betting you will find they have a bad cell or
> cells.
>
> They will show reasonable voltage but when you place a demand on them
> (amperage) they are breaking down internally.
>
> This happens up here all the time in winter conditions, the electrolite in
> the battery will freeze and expand when its really cold, causing the
> internal plates to buckle and touch each other causing internal shorts.
>
> Battery casings that are bulged out at the sides are normally a good
> indication this has occured.
> --
>
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| Re: [GMCnet] What a Day! [message #77574 is a reply to message #77568] |
Sun, 21 March 2010 21:06 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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No, I don't have a clue why I've had two failures. Especially since the
electrical source -- the alternator -- is different in the two cases. It's
especially mystifying when you see in the schematic that about the only way
to damage a driver would be with a severe over-voltage input -- and even
that should take out the protective Zener first (as happened in my previous
failure, but not obviously in this one).
One thing I have not checked is my Progressive Dynamics -- it has been the
power supply for a lot of the time both ECU's were installed, but there's
been not other indication of a problem with it.
Ideas anxiously awaited -- before I blow up another ECU! :-)
Can it be testing me just because it heard of my EE education? If so, I'll
gladly confess that I've forgotten most of that!
Ken H.
On Sun, Mar 21, 2010 at 9:48 PM, Mr.erf ERFisher <mr.erfisher@gmail.com>wrote:
> :-( That means the
>
> > ECU's driver for the right injector has failed.
> >
> > This is really strange. 10 years we have been running stock 7747s' and I
> have never heard of a failure from all of us using these, even getting them
> from junk yards, they have been bullet proof.
>
> It seems to me you have had two driver failures since you started this
> saga,
> any idea what could cause this ?
>
> gene
>
>
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| Re: [GMCnet] What a Day! [message #77598 is a reply to message #77574] |
Sun, 21 March 2010 23:43 |
Ron
Messages: 250
Registered: February 2004
Location: Conifer, Colorado
Karma: 0
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Senior Member |
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Ken..
You remember a hell of a lot more than I ever knew..
I thought Zender was an Ice Cream flavor... 
Ron
now a P.O.
Conifer, CO
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